90% red - no one lives there, or not in the union anymore
70% red - nearly uninhabited
50% red - large population decrease
50% blue - moderate population increase
70% blue - major population increase
90% blue - huge population increase
Terrorists from Saudi Arabia and Egypt detonate multiple giant thermonuclear warheads in NY, DC, and VA. Those states, along with MA, CT, RI, NJ, WV, MD, and DE, become completely uninhabitable due to the resulting radioactive fallout. The states of ME, NH, VT, PA, OH, KY, TN, and NC are nearly entirely evacuated shortly thereafter either to Canada or to neighboring states in fear of their becoming contaminated with radiation as well. The capital of the United States, with DC completely obliterated, is hastily moved to Omaha, Nebraska. This results in a massive population influx into Nebraska as people go there in an attempt to feel safe and secure in frightening times.
Taking advantage of the mass confusion caused by these brazen terrorist attacks, the Mexican army launches a surprise invasion of TX, which falls due to a lack of preparedness and due to a complete lack of communication that results in an inability to mobilize an effective force to counteract the invasion. The Mexican army continues through NM, AZ, NV, and CA, before a ceasefire is finally signed. The conquered states are added to the territory owned by Mexico. In conjunction with these attacks, Russia invades and reclaims AK, and Japan conquers HI. Given that most of CA had not been completely occupied at the time of the ceasefire, most of the citizens of northern CA flee to WA or OR.
Meanwhile, while global warming is eventually taken under control, the people of Louisiana were still dumb enough still to inhabit their state before that occurs, and a massive hurricane floods New Orleans yet again. With Mexico at their doorstep to the west and huge floods to their east, most of the population is all like "screw this" and hightails it to Arkansas.
Because federal funding to the states was almost entirely cut off in light of the terrorist attacks, Mississippi quickly descends to be on par with your average African country in terms of literacy, health, and education, so almost all of its citizens flee for greener pastures shortly thereafter. Because the only people who were unable to flee were the poorest of the poor, Mississippi began to further resemble your average African country as a result.
Meanwhile, Raul Castro turns out to be a real jerk in Cuba as he takes over from Fidel at last, so the entire population moves to Florida, making it the new most populous state by far.
Finally, ID, MT, WY, ND, and SD see a big population outpour as all of their residents finally wake up to the fact that their states suck and are dumb.
